1. Field of the Invention
The present invention relates to the use of binding members which bind to both Lewisy and Lewisb haptens in the treatment of tumours and leukaemia.
2. Description of the Related Art
The Lewis antigens, which include Lewis y, b, x and a antigens, are blood group antigens. The Lewisy hapten is a difucosylated tetrasaccharide (Fuc 1-2Galβ 1-4(Fucα 1-3)GIcNAc found on type 2 blood group oligosaccharides. This antigen is a positional isomer of the Lewisb hapten (Fuc1-2Galβ1-3(Fucα1-4)GINAc and a fucosylated derivative of the Lewisx hapten. The Lewisy hapten is a cell surface antigen epitope which is expressed by colorectal tumours (Abe et al., Cancer Research, 46, 2639 (1986); Kim et al., Cancer Research, 46, 5985 (1986)).
The mouse monoclonal antibody C14 was raised to the C14gp200 antigen. The mouse monoclonal antibody C14 recognises Lewisy hapten (Brown et al, Biosci. Rep. 3, 163 (1983); Brown et al., Int. J. Cancer, 33, 727) and binds to 78% of colorectal cancers (Durrant et al., J. Natl. Cancer Inst., 81, 688 (1989)).
Other antibodies which bind to the Lewisy hapten are known. For example, EP-B-0285059 discloses an antibody, BR-55, which reacts with both Lewisy and B-7-2. B-7-2 has also been shown to be associated with tumour cells (EP-B-0285059). EP-B-0285059 states that the advantage of recognising two cancer-associated epitopes is that it increases the chances of recognising more tumour cells relative to normal cells. However, BR-55 relies on effector cells in order to be able to kill cells.
In addition, US55869045 discloses an antibody, BR-96, which binds to both Lewisy and Lewisx haptens. Although US5869045 teaches that antibodies which kill cells by themselves are rare, BR-96, has been shown to have the ability to kill cancer cells in unmodified form (US5869045). Since no other Lewisy antibody has been reported to cause direct cytotoxicity, the activity of BR-96 can be assumed to be related to its recognition of the Lewisx hapten.
Antibodies which bind to both Lewisy and Lewisb antigens are known. Studies have demonstrated that C14 monoclonal antibody recognises and binds to both Lewisy and Lewisb (extended and non-extended forms) antigens (Durrant et al., Hybridoma, 12, 647-660 (1993)). A C14 monoclonal antibody specific for both Lewisy and Lewisb antigens was raised against primary colorectal tumour cells using standard fusion protocols. The C14 antibody recognised a range of solid tumours but as it was an IgM, it was not very useful in reproducibly screening large numbers of serum samples. One of the immunological characteristics of carbohydrate antigens is that they usually elicit a T cell independent response, resulting in the production of an IgM antibody.
Subsequently, an anti-idiotypic approach in mice was used to produce an IgG variant of the C14 (IgM) monoclonal antibody. Rats were immunised with C14 monoclonal antibody and rat anti-C14 monoclonal antibody was purified. Immunisation of mice with the rat anti-C14 antiserum and the C14gp200 antigen and subsequent fusion of the immune splenocytes with a mouse myeloma produced five IgG (two IgG3s and three IgG 1s) monoclonal antibodies recognising the Lewisy and Lewisb antigens (Durrant et al., Hybridoma, 12, 647-660 (1993)). Each of the five IgGs (referred to as the “692” monoclonal antibodies) demonstrated the same specificity as C14 (Durrant et al., Hybridoma, 12, 647-660 (1993)). These antibodies were shown by thin layer chromatography and ELISA to bind to extended and non-extended Lewisy and Lewisb haptens but not to Lewisx or H blood group hapten. The antibodies bound to breast, lung, colorectal, gastric, and ovarian tumours and myeloid leukaemia. Recognition of normal tissue was minimal and restricted to weak staining of the upper gastrointestinal tract basement membrane, mucin staining of stomach and fallopian tubes and weak staining of liver capillaries.